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Regioselective Formation of β‐Alkyl‐α‐phenyliridabenzenes via Unsymmetrical 3‐Vinylcyclopropenes: Probing Steric and Electronic Influences by Varying the Alkyl Ring Substituent
Author(s) -
Wu HePing,
Weakley Timothy J. R.,
Haley Michael M.
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400893
Subject(s) - regioselectivity , substituent , alkyl , steric effects , chemistry , isomerization , ring (chemistry) , electronic effect , medicinal chemistry , stereochemistry , catalysis , organic chemistry
The synthesis of unsymmetrical ( Z )‐1‐alkyl‐3‐(2‐iodovinyl)‐2‐phenyl‐1‐cyclopropenes (R=Me ( 8 a ), Et ( 8 b ), i Pr ( 8 c ), and t Bu ( 8 d )) and their reactions with Vaska's complex [Ir(CO)Cl(PPh 3 ) 2 ] and its trimethylphosphine analogue [Ir(CO)Cl(PMe 3 ) 2 ] were investigated. Iridabenzvalene ( 13 / 20 ), iridabenzene ( 14 / 21 ), and/or η 5 ‐cyclopentadienyliridium complexes ( 15 / 22 ) were obtained in modest yields and were fully characterized by spectroscopic means. X‐ray structural data was secured for iridabenzvalene 13 d and iridabenzenes 14 a,b,d . Whereas iridabenzenes 14 a – c were stable at 75 °C for 48 h, 14 d , which possesses a bulky t Bu group, rearranged cleanly to cyclopentadienyliridium 15 d at 50 °C over 15 h and displayed first‐order kinetics. The influence of the alkyl substituent on the mechanisms of iridacycle generation, isomerization, and iridabenzene regioselectivity is discussed.